Rocktown Natural Area

Mixed Grass Praire

Native grasslands of the Great Plains are generally classified as short grass, tall grass, or mixed grass prairies. In the early 1800’s, prior to westward expansion, the midwest and western states contained millions of acres of all three types of prairie. Today, only a small percentage of those acres remain ecologically intact. The lowland valley area on the west end of the lake on KDWPT lease contains a substantial number of concentration of native grass and forb species that constitute the mixed grass prairie. These species include Little Bluestem, Big Bluestem, Switchgrass, Indian Grass, Blue Gramma, Buffalo Grass, and Sideoats Gramma. This is an important prairie resource for the state of Kansas.

Rocktown Natural Area

Rocktown Natural Area is a 305 acre site located on the western boundary of Lucas Park. In August, 1986 it was designated a Natural and Scientific Area by the Kansas Biological Survey. Although the most obvious feature of Rocktown is the 15-30 foot high sandstone pillars that dominate the landscape, it is the unusual mix of prairie plant species associated with the shallow, sandy soils of the Sandhills that paramount natural significance. The soils in the area are not typical of this region of Kansas. Dakota sandstone and limestone outcrops are common. Plant species of interest include Fremont’s clematis, Fremont evening primrose, shortstem spiderwort, blue funnel lily, Buckley’s penstemon, fameflower, prairie sandreed, and Maryland senna. Although of interest, these species are not sufficiently rare or unusual enough to require monitoring by the Kansas Natural Heritage Inventory. Rocktown is, however, a significant state resource.

Fossil Resources

The Dakota Sandstone is an extensive geologic formation found throughout the Great Plains region. A once vast, warm shallow sea that covered much of Kansas contributed to the creation of the rolling hills and deposited plant/seashore materials and creatures creating the sandstone, limestone, and fossils it left behind. At Wilson Lake the sandstone formation is exposed in several areas. These exposures have proved to be excellent sources of fossil material dating back to the Cretaceous era, approximately 80 million years ago. The most notable areas for fossil remains within the project area are along Southshore Drive, near the dam spillway and north of Bunker Hill.

Fossils represented at Wilson Lake include a variety of plant material and large ammonites. The fossil plant material is associated with nodules from the Dakota Sandstone formation. Although these nodules were once abundant on the surface of the ground, pilfering over the years has greatly diminished their number. Ammonites, extinct relatives of octopi and squid, are flat, spiral fossil shells of cephalopods, which were especially abundant in the Mesozoic age. Neither the nodules with the associated plant fossils, nor the ammonites are particularly rare or unusual. Both are relatively common throughout the extensive area of the Great Plains region.

Many ancient sharks teeth have been found. One dinosaur fossil belonging to a Silvisaur (closely related to the Ankylosaur), was discovered at Wilson Lake in 1988. The fossil was found near the middle of the lake on land SE area of Lucas Park, which is exposed when the water is at a relatively low level. (Dr. Michael Nelson FHSU, personal communication). Sternberg Museum believed the dinosaur died at the shoreline of the once warm shallow sea and bloated and floated to its 1988 location b/c dinosaurs were only present during the time frame that this area was under sea. They found a mold of a sacrum vertebrae. Minerals collected around the vertebrae and over time the bone deteriorated and left the mold that was cast.

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